THEORY AND IMPROVEMENTS FOR SNMS DEPTH PROFILING WITH INA3

Optimization of SNMS depth profiling using the direct bombardment mode (DBM) is possible by improvement of the ion current density distribut ion, reduction of bombardment energy and independent choice of current density. A model for primary ion extraction is presented and ion curr ent density distributions have been calculated for different sample ho lder arrangements. Using the simulation procedure optimal extraction c onditions can be predicted for conventional arrangements and suggestio ns for new ones can be made. The best depth resolution has been obtain ed using a new extraction arrangement with an additional aperture.